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MWe asked vendors to demonstrate interoperability on three levels, ranging from a basic call completion between two endpoints to gatekeeper-to-gatekeeper communication across domains. Vendors selected the scenario that best suited their equipment. To participate in our interoperability event, vendors had to prove interoperability with at least two products from other vendors.

In the most basic level of testing, we asked vendors to establish a phone call between their product (an IP phone, IP soft phone or IP PBX) through a gateway (such as Cisco's AS5300 or Clarent's Gateway 400) to a terminating point on the public switched telephone network (PSTN). Communication between the gateway and the PSTN was via T-1 trunk, through an Adtran TSU-100, to an analog line and analog phone on the terminating end of the communications path.

The gatekeeper was introduced in the second level of testing. Optional in the H.323 standard, the gatekeeper provides address translation, admissions control, bandwidth control and zone management to a collection of devices under its control. Products tested in this scenario might include gateways, IP phones or PCs supporting soft phone applications. In this scenario, calls were placed between one endpoint through a gatekeeper to another end node - a gateway (from the vendor originating the call or another vendor), or another endpoint (IP phone, analog phone from another vendor).

The third level of testing required gateway-to-gateway communications across H.323 zones (or domains). In this test, one vendor's originating gateway or gateway/gatekeeper combination product placed a call to another gateway and/or gatekeeper (its own or another vendor's) through a gatekeeper (again, its own gatekeeper or one from another vendor). To cross domains, communication between two gatekeepers (from the same vendor, or between one vendor and another vendor's product) was required.

In the tests, calls were considered successfully placed if a voice path was established between both parties, the voice call was understandable and the calls closed gracefully so that network resources were fed quickly and available to subsequent callers. Miercom engineers also monitored post dial delay.

This story, "Miercom VoIP test scenarios" was originally published by
Network World.